Gasification and melting system technology with wide application to the treatment of waste such as municipal waste and also incombustible waste, burned residue, and sludge is known. Such gasification and melting systems are provided with: a gasification furnace that gasifies waste by thermally decomposing the waste; a melting furnace that combusts pyrolysis gas generated by the gasification furnace at high temperatures and converts ash contained in the gas into molten slag, the melting furnace being disposed downstream of the gasification furnace; and a secondary combustion chamber that combusts flue gas discharged from the melting furnace. To achieve the recycling, volume reduction, and detoxification of waste, gasification and melting systems allow the slag extracted from the melting furnace to be used for construction material such as road bed material. Gasification and melting systems recover waste heat from the flue gas discharged from the secondary combustion chamber to generate electricity.
A fluidized bed gasification furnace is widely used as the gasification furnace of such a gasification and melting system. At the bottom of such a fluidized bed gasification furnace is formed a fluidized bed that is a fluid medium being fluidized by the supply of combustion air. Fluidized bed gasification furnaces are devices that partially combust the waste fed to the fluidized bed and thermally decompose the waste in the fluidized bed maintained at high temperatures by combustion heat.
Additionally, fluidized bed gasification furnaces are configured to discharge sand, which is the fluid medium, and incombustibles from the bottom of the furnace. A need exists for such a gasification melting facility to be capable of volume reduction. The reduction of incombustibles, which ultimately end up as landfill, is a matter of importance. Known means of reducing the volume of incombustibles that ultimately end up as landfill include methods of recovering valuable metals such as iron and aluminum contained in the incombustibles.
Another example of means of reducing the volume of waste is a gasification melting facility described in Patent Document 1, in which the fluid medium is separated from residues at the bottom of the fluidized bed gasification furnace, and the fluid medium is recovered to be reused. The metals contained in the residues at the bottom are sorted and collected. The non-metals are reused after pollutants are removed from the surface via abrasion. Patent Document 1 also describes technology of conveying pulverized non-metals to the melting furnace via airflow.